12. Respiration Basics

Question 1

Uses of Energy in the Body

Answer 1

• Respiration is a chemical process that involves the breakdown of nutrient molecules (specifically glucose) in order to release the energy stored within the bonds of these molecules
• Respiration can take place with oxygen (aerobically) or without oxygen (anaerobically). Much less energy is released for each glucose molecule broken down anaerobically compared to the energy released when it is broken down aerobically
• Respiration occurs in all living cells. Most of the chemical reactions in aerobic respiration take place in the mitochondria

Question 2

Use of Energy (PIC)

Answer 2

Question 3

How is Respiration Controlled?

Answer 3

Respiration is a series of reactions that are controlled by enzymes.

Question 4

Aerobic Respiration

Answer 4

• Aerobic respiration requires oxygen and is defined as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy
• It is the complete breakdown of glucose to release a relatively large amount of energy for use in cell processes
• It produces carbon dioxide and water as well as releasing useful cellular energy

Question 5

Aerobic Respiration Balanced Equation

Answer 5

Question 6

Investigating Uptake of Oxygen by Respiring Organisms

Answer 6

• We can investigate aerobic respiration in living organisms by measuring the amount of oxygen that they take from the air
• This is done by measuring the change in volume in an enclosed tube containing the organisms
• However, as they respire the organisms release carbon dioxide, which increases the gas volume
• The carbon dioxide must therefore be removed from the tube using a chemical like soda lime or sodium hydroxide, otherwise it will make the experiment results inaccurate
• Any small organisms can be used in the apparatus, including seeds or arthropods
• The apparatus (shown below) is known as a respirometer
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Question 7

What is a control?

Answer 7

• A control is a duplicate experiment set up with the condition being investigated having been removed or neutralised in some way.
• In the experiment above, the control is the glass beads.
• As they are not alive, they will definitely not be respiring. If the volume of oxygen decreases in the tube with the glass beads during the course of the experiment, then we know that the condition being investigated (respiration in living organisms) is not the cause of it.
• So, a control helps to make your experiment valid.

Question 8

Investigating the Effect of Temperature on the Rate of Respiration

Answer 8

• To investigate the effect of temperature on the rate of respiration of germinating seeds the respirometer can be set up and the tubes submerged in a series of water baths set at different temperatures, eg 10℃, 15℃, 20℃, 25℃, 30°C
• The seeds should be kept in the water bath for 15 minutes before the start of the experiment to ensure they have acclimated to the temperature
• As respiration is an enzyme controlled reaction, it is unlikely to work faster beyond around 40℃ as the enzymes will denature

Question 9

Anaerobic Respiration

Answer 9

• Anaerobic respiration does not require oxygen and is defined as the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen
• It is the incomplete breakdown of glucose and releases a relatively small amount of energy for use in cell processes
• It produces different breakdown products depending on the type of organism it is taking place in
• You need to know the equations for anaerobic respiration in humans (animals) and the microorganism yeast

Question 10

Anaerobic Respiration in Animals

Answer 10

• Anaerobic respiration mainly takes place in muscle cells during vigorous exercise
• When we exercise vigorously, our muscles have a higher demand for energy than when we are resting or exercising normally. Our bodies can only deliver so much oxygen to our muscle cells for aerobic respiration
• In this instance, as much glucose as possible is broken down with oxygen, and some glucose is broken down without it, producing lactic acid instead
• There is still energy stored within the bonds of lactic acid molecules that the cell could use; for this reason, less energy is released when glucose is broken down anaerobically

Question 11

Anaerobic Respiration in Yeast

Answer 11

We take advantage of the products of anaerobic respiration in yeast by using it in bread making(where the carbon dioxide produced helps dough to rise) and in brewing (where the ethanol produced makes beer)

Question 12

Anaerobic Respiration Balanced Equation in Yeast

Answer 12

Question 13

Comparison of Aerobic & Anaerobic Respiration

Answer 13